Conventionally, a navigation system that displays a lane guide map showing the direction of each lane formed on a road with an arrow is known. This conventional navigation system determines the direction of each lane which is to be displayed on such a lane guide map with an arrow on the basis of the actual geometry of roads. Therefore, for example, in a case of an intersection in which a main road curves rightwardly and a bypass branching off from the main road extends in a straightforward direction, a lane guide map in which the bypass is shown by a straightforward arrow and the main road is shown by an arrow bent toward a diagonal right direction is displayed. In this specification, the term “intersection” is used as a concept including a crosspoint where a plurality of roads intersect and a branch point where a road branch off from another road.
As a technology of displaying such a lane guide map, patent reference 1 discloses a navigation apparatus that can surely support a case in which a vehicle travels along a road having many numbers of lanes and has to make a lane change to pass through an intersection at a predetermined distance or less before reaching an intersection for guidance. This navigation apparatus includes an information storage means for storing lane information data about lanes at each intersection, a display means for displaying the lane information, and a display control means for displaying the lane information data about lanes at each intersection on the display means on the basis of the lane information data stored in the information storage means, and the display control means judges whether or not there is another intersection which the vehicle has to pass through at a predetermined distance or less before reaching an intersection for guidance, and, when there is another intersection which the vehicle has to pass through, controls to display the lane information about the other intersection which the vehicle has to pass through and the lane information about the intersection for guidance.    [Patent reference 1] JP, 2000-251197, A
A problem is however that in the lane guide map displayed by the above-mentioned conventional navigation system, a discrepancy may occur between the direction of each lane displayed on this lane guide map with an arrow and the direction of each lane which the driver recognizes. In the above-mentioned example in which for an intersection in which a main road curves rightwardly and a bypass branching off from the main road extends in a straightforward direction, a lane guide map in which the bypass is shown by a straightforward arrow and the main road is shown by an arrow bent toward a diagonal right direction is displayed, there is a case in which the driver has an illusion that the straightforward arrow shows the main road and the diagonal left arrow shows the bypass.
Furthermore, because the angle between an incoming road coming into a branch point on a highway and an outgoing road extending from the branch point is small in many cases, it is difficult to clearly determine the direction of each lane at the branch point, such as a straightforward direction, a diagonal right direction, or a diagonal left direction, from this angle. Therefore, a problem is that the directions of all lanes at an intersection for guidance may be expressed as straightforward arrows in the lane guide map displayed by the conventional navigation system.
The present invention is made in order to solve the above-mentioned problems, it is therefore an object of the present invention to provide a navigation system and a lane information display method capable of displaying a lane guide map which meets users' feeling.